1. Field of the Invention
The present invention relates to a method for operating a motor vehicle, and more specifically to a method for operating a vehicle having a start/stop system.
2. Description of Related Art
Commercially available engine control systems, also referred to as stop/start systems, start/stop systems, or automatic start/stop systems reduce fuel consumption in stationary phases of motor vehicle operation. For example, when stopped at a traffic light, in particular in city traffic, in a stationary state under certain conditions the engine is automatically shut off and restarted. In vehicles having a manual transmission with a manually activated clutch, upon selecting an idling position and engaging the clutch, i.e. releasing the clutch pedal, a control unit shuts the engine off. Upon activating or depressing the clutch pedal, the control unit restarts the engine.
Besides conserving energy or fuel, and the associated emission of pollutants, such support and assistance systems may increase operation and comfort. In one example, the vehicle includes a hill holder or hill holder assist system providing automated assistance and reducing vehicle rollback when starting on inclines.
Such systems hill holder or hill start assist systems use at least part of the existing brake system to hold the vehicle temporarily on the incline by activating the vehicle brakes. Automated transmissions provide the advantage over manual transmissions in that, depending on the situation, they provide at least a low creeping torque. In contrast, when placed on an inclined and the automated or manually activated clutch separates, is in a decoupled state, a vehicle can roll forward or back a significant distance. In particular, when on severe inclines, this movement may entail an increased feeling of a lack of safety or increased stress in the driver.
A vehicle brought to a stop on a gradient, with a standard transmission and an automatic start/stop system, can roll after the vehicle stops and the brake pedal has been released but before the drive engine is started. Although generally confusing for the driver of the vehicle, it is also surprising as the driver is not used to such movement when the vehicle has a hill holder system. While such systems should avoid such situations, rollback or movement can happen because such systems are not activated at a predefined clutch position. The result being a risk that the hill holder or hill start assist system has a delayed start whereby the vehicle may roll back if the brake is released too quickly and/or the clutch is disengaged after a delay.